Drosophila tumor suppressor genes have been shown to cause tumors in the larval brain and imaginal discs. Tumors in the brain have been determined to arise due to a disruption in neuroblast/neuron proliferation and differentiation. In the tumor suppressor gene, lethal giant larvae, disruption of apical basal polarity of the neuroblast stem cell leads to an increase in neuroblast self-renewal at the expense of ganglion mother cells and neurons. Tumors from lethal giant larvae mutants are metastatic upon transplantation into adult Drosophila hosts. The goal of the project is to determine the factors that are responsible and required for metastasis of a subset of the tumor cells. We have undertaken a deficiency screen to study the Drosophila genome in order to determine regions which contain genes important for metastasis. Preliminary results indicate the region 3L 69F6-70A2 contains one or more genes important for metastasis and/or tumorigenesis of lethal giant larvae tumors. . A genomic deficiency with these breakpoints combined with the lethal giant larvae mutation causes a reduction of over 70% in the metastatic index of the tumors compared to lethal giant larvae tumors. We are testing three genes mapped to the chromosomal region, tartan, syntaxin 13, and CG11279 for a role in metastasis in our model system. Furthermore, we are developing GFP-marked tumor suppressor mutant stains in order to study metastatic cells compared to non-metastatic primary tumor cells in Drosophila using genome arrays. We have made Drosophila tumor suppressor strains that contain GFP and CD8 under the control of the UAS/GAL 4 expression system with expression in the larval brain. The GFP allows for visualization of the tumor or metastasis and gross dissection, while the CD8 marker can be used for biochemical purification of the CD8+ tumor cells following preparation of a single cell suspension. Whole transcriptome comparison of lethal giant larvae primary tumors with metastases can identify pathways or groups of genes activated in the metastatic process. Follow-up genetic analysis in the model will provide verification of these results.